High voltage stepper drivers?

Hi, I've been making my brain hurt looking at stepper motors, torque ratings,
etc. but I've noticed something a bit odd.

It appears that to get the best performance from a stepper it should be driven at ~20 times its rated voltage, or 32 times the square root of the coils inductance in mH (this makes more sense considering the step input voltage / current curve of an inductor).

Looking at several motors in the 1.8 to 3Nm range this would equate to a driving voltage of around 60 to 100V, but most (cheap) drivers seem to have output voltage limits of around 35 - 48V, which would imply not getting the best from the motors.

Anyone know of any drivers with higher voltage capability available in the UK that don't cost an arm and a leg?

I know drivers are available like the MCP MSD980 - 7.8A @ 90V, but £105+VAT per axis is too steep for me at the moment. :(

I look forward to any information you can share.

Thanks for that, I've been trawling EBay looking for bargains, but I hadn't thought to try the non-UK versions of the site.

Following the link you gave I found a much more reasonable 3 axis driver kit that does 60V @ 5A, but nothing higher.

Time to hit the books again to try and find out how much lower voltages hurt performance :(.

5A is fine for most sensible steppers up to around 12Nm, it's the voltage I want higher, to play it safe with voltage spikes on the mains supply I'd have to drop to 10+% below the max voltage, or invest in a regulated supply. And that would drive the cost up again :(.

I thought on imports the tax was just paying the VAT? (Unless I get it sent marked as a gift :D).

Voltage makes a differnece to top speed performance, but do you need it?
You mention 1.8-3 Nm, so you are within the Nema 23 range, so look for a motor that is as high current as possible, to keep the inductance as low as possible.
There are disadvantages to high voltage as well; the motor will get a lot hotter, and will make a lot more noise.
In my experience for a nema 23 motor 40-50 V is fine, and going up to 70 V will only give you a performance increase at the higher speeds. (Over 300 RPM)
Do you want to pay 50-60% more for 15-20% more performance?
What torque and speed do you need?
Nema 34 motors are different, and these really need high voltage to get the best from them.

Thanks Gary, food for thought there. I agree higher current, lower inductance motors have lower voltage requirements as well.

Slightly confused as to higher voltages causing more noise :confused: why would this be?

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The more I learn about this hobby, the brighter the light of knowledge grows, the deeper is the pit of ignorance revealed...

I am not sure why it makes more noise, will have a look into it and post later.

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Originally Posted by ZeroCount

Thanks Gary, food for thought there. I agree higher current, lower inductance motors have lower voltage requirements as well.

Slightly confused as to higher voltages causing more noise :confused: why would this be?

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The more I learn about this hobby, the brighter the light of knowledge grows, the deeper is the pit of ignorance revealed...

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